System for drafting fibrous materials



Nev. 27, 1956 J, M. B. AYMERICH 2,771,639

SYSTEM FOR DRAFTING FIBROUS MATERIALS Filed May 28, 1951 2 Sheets-Sheetl Nov. 27, 1956 J. M. B. AYMERICH 2,771,63Q SYSTEM FOR DRAFTING FIBROUSMATERIALS Filed May 28, 1951 2 Sheets-Sheet 2 INVENTOR, aw; MATE/AEascw-Aymmwcw United States PatentO SYSTEM FOR DRAFTING FIBROUSMATERIALS Jose Maria Bosch Aymerich, Barcelona, Spain Application May28, 1951, Serial No. 228,586 Claims priority, application Spain July 3,1950 2 Claims. (Cl. 19-130) The invention relates to a method andmechanism for drafting cotton and other fibrous materials in spinningand roving frames.

The drawing out of rovings or slivers has been performed in apparatuswhich essentially consists of two pairs of rolls. The one pair comprisesthe feed rolls which revolve at relatively low speeds and feed a sliverof a certain weight per unit of length, and the other pair comprises thedrawing rolls which revolve at a higher speed than the feed rolls anddraws out the strand of fibers received from said feed rolls. The lengthof the produced draft corresponds to the difference between theperipheral speed of the feed rolls and that of the drawing rolls.

In the first stages of the development of drafting apparatus, thedesired stretch was obtained by a series of separate drafting mechanismswhich each stretched the fibers to about 3 to times their length priorto drawing. When greater drafts were intended the fibers in the sliverspread out in different directions which produced weak spots and breaks.Such breaks required a continuous supervision of the spindles, i. e. anincreased number of operators. Therefore, it was considered moreeconomical to use a greater number of drawing frames producing a limiteddraft instead ducing a longer draft.

In order to increase the efficiency of the work of these machines and toavoid an excessive number of successive drafting steps independent ofeach other, the so-called long draft system was developed. A fundamentalproblem in the development of said system concerned the guiding of thesliver on its way between the two pairs of rolls, i. e. in the zonewhere the actual stretching is carried out, and various solutions ofthis problem have been suggested. Many of the proposed devices weremodifications of the idea to provide so-called draft aprons which guidedthe fibers wholly or partially in a portion of the draft zone anddelivered them near the nip of the draft rolls.

Another mechanism for reducing the number of spinning steps was based onthe general idea of providing drawing devices with three and four pairsof rolls, so as to divide the total draft into two steps within'a singleapparatus. The first step produced a preliminary draft, suitable to takeout the twist which the entering sliver may present, and the second stepwas arranged to effect maximum elongation.

The advantages of these modern drawing mechanisms are obvious and the"long draft system has been widely introduced in spinning mills.Nevertheless, quite a number of problems remain, which have not beensatisfactorily solved so far.

The two-step drafting mechanisms present the drawback that the fibershave the tendency to leave the first draft stage in a somewhat spreadout and dispersed condition, and this condition is accentuated duringtheir travel to and through the second stage: therefore. they enter thesecond stage under conditions unfavorable to the drawof fewer framesproing, as they are weaker and/or lack the twist which the slivernormally had when processed according to the old method in a pluralityof seperate drawing mechanisms. Many solutions have been proposed forobtaining a compression or a guided travel of the sliver on its way fromthe one to the other drawing step. The devices designed for this purposecomprised either rigid and fixed surfaces or endless belts of flexiblematerial or other means which rendered the apparatus excessivelycomplicated and involved high operating cost of the machine;objectionable long interruptions in the delivery of each spindle wereunavoidable when a breakage in the sliver occurred.

Draft aprons present an efficient guiding means, but because of theirelastic composition they are subject to deformations and elongationsand, therefore, inherently unable to ensure completely uniform workingconditions and rate of travel over prolonged periods of time.

Other proposals were directed to the recovery of the fibers which hadstrayed out or flared during the first drawing step.

Cleaning rolls were provided in order to avoid clogging of the drawingroll of the first draft stage, and/0r specific means were arranged todeliver the fibers in a more condensed condition to the second drawingstage. However, all those designs did not give a complete solution ofthe problem of maintaining a complete control of the fibers in amulti-stage drafting mechanism.

A principal object of the invention is to provide a long draft system inwhich the sliver leaves the drawing rolls of the first drafting stage asa compact, uniform strand of fibers.

Another object of the invention is to provide means which ensuremaintaining said compactness and uniformity of the sliver on its travelfrom the drawing rolls of the first drafting stage to the seconddrafting stage.

Still another object of the invention is to provide means which feed thesliver to the second drafting stage as a compact strand of parallelfibers so as to prevent the rolls from being clogged by loose strayfibers. Such obstruction disturbs the smooth operation of the draftingmechanism.

Other objects and advantages will become apparent from a considerationof the specification and claims.

In the conventional lon -draft mechanisms, the stray fibers werecondensed in the space comprised between the drawing roll of the firstdrafting stage and the feed roll of the second drafting stage; or to putit in a more generic language, the aim was to rearrange the fibers inthe zone comprised between the two drafting stages, i. e. where thedraft or stretch is nil or practically negligible.

In contradistinction thereto, the aim of the present invention is not torearrange the fibers after they have strayed out but to avoid theirstraying out at all. In other words, the aim is not to correct theresult but to eliminate its cause, which allows of attaining much longerdrafts. According to the invention, any twist still present in thedelivered sliver is eliminated in the first drafting stage and thisuntwisting operation i effected simultaneously with guiding andcondensing manipulations, which are applied during the first draftingstage, thereby avoiding the spreading out of the fibers that otherwisewill surely occur when the sliver loses its twist. Subsequently, thetransfer of the fibers from the first to the second drafting stage ispositively guided and the sliver travels during said transfer at alltimes over one or more cylindrical rigid and convex surfaces whichrevol've at aperipheral speed substantially equal to the rate of travelof the sliver before it is subjected to the action of the seconddrafting stage, In this way, I avoid all irregularities which areproduced by enclosing the sliver between surfaces movingat a .spee ddiiferem from the rate of travel of the sliver or between very elasticsurfaces which readily deteriorate and easily may produce irregularitiesin the obtained yarn.

The aim of the invention is attained by arranging a condensing elementbetween the feed rolls and the draft rolls of the first drafting tage;this element keeps the fibers in parallel alignment at a point of theirtravel where they would otherwise stray out following their untwisting,and it guides or leads the fibers in said parallel alignment to thetangency line of the draft rolls.

One or more guiding rolls are provided which positively guide the sliverfrom the draft rolls of the first draft stage to the feed rolls of thenext draft stage in uch a way that the sliver is at all times supportedby roll surfaces. Therefore the fibers never travel unsupported throughfree space but are always supported by cylindrical surfaces. In thisarrangement, the sliver is positively guided by a series of guidingrolls, whereby the first roll of such series is formed by one of thedraft rolls of the first draft stage and the last guiding roll isconstituted by one of the feed rolls of the next draft stage.

The positively driven feed roll of the second or fol lowing draft stepsshould have a slightly higher peripheral speed than the positivelydriven draft roll of the preceding stage; consequently, the sliver issubjected to a very slightly increased rate of travel over the guidingrolls between two consecutive draft stages and the fibers of the sliverare held wholly in line with the path of the sliver and parallel andattached to the roll surfaces.

The guiding rolls are so arranged as to maintain the direction of travelof the sliver, and they should exert by their weight a slight pressureon the sliver at the tangency line with the contacting rolls. In thisway, the fibers in the sliver have the possibility to slip, which isuseful in drafting very long fibers.

If several guiding rolls are provided, each alternate roll should have agrooved or fluted surface.

In a specific, particularly simple and economic embodiment of theinvention, the function of the guiding rolls, i. e. the positiveuninterrupted guidance of the sliver between two consecutive draftstages, is taken over by the rolls of the drawing mechanism proper, i.e. by one of the draft rolls of the first drawing stage and by one ofthe feed rolls of the second drawing stage. For instance, the bottomdraft roll of the first drawing stage and the top feed roll of thesecond drawing stage, or inversely the top draft roll of the firstdrawing tage, and the bottom feed roll of the second drawing stage, mayact as such guiding rolls; in both cases, said rolls play a double rolesimultaneously, as guiding roll and as draft roll or feed roll,respectively.

If the system of guiding revolving rolls consists of more than tworolls, the first and last roll will assume the same double function asoutlined hereinbefore.

The invention will be readily understood from the following descriptionin connection with the accompanying drawings which show someillustrative embodiments of the invention. In the drawings:

Fig. l is a diagrammatic vertical sectional view of a drawing mechanismembodying the invention;

Fig. 2 is a diagrammatic perspective view of the elements shown in Fig.1, wherein however the rolls are not shown in their true sizerelationship in order to present a better view of the mechanism;

Fig. 3 is a diagrammatic vertical sectional view of another embodiment;

Fig. 4 is a vertical sectional view of still another embodiment of theinvention, showing three draft stages, and

Fig. is a vertical sectional view of a mechanism similar to that shownin Figs. 1 and 2.

In the drawings, 1 represents the sliver before entering the drawingmechanism, and 2 the sliver after drawing, 3 and 4 are the feed rolls,and 5 and 6 the draft rolls of the first preliminary draft stage.

The final draft is obtained in the roll pairs 7, 8, 9, and

10, of which 7 and 8 represent the feed rolls and 9 and 10 the draftrolls.

In a three-stage drawing mechanism (Fig. 4), the last stage isrepresented by the feed rolls 17 and 18 and the draft rolls 19 and 20.The zone between the second and third drawing stage extends normallyfrom 24 to 25, although the drafting action can be extended beyond thecorresponding feeding cylinders.

As usual in mechanisms of this kind, the preferably grooved or flutedbottom rolls 4, 6, 7, it), 17, and 19 are positively driven, and the toprolls 3, 5, 8, 9, 18 and 2t are covered with some cushioning material,such as leather, cork, rubber, or the like, and frictionally driven fromthe bottom rolls. The drawing rolls 6 and 10 are driven at a greatlyhigher peripheral speed than the corresponding feed rolls 4 and 7, so asto obtain the desired draft. The bottom feed roll 7 of the second draftunit is preferably driven at a very slightly higher peripheral speedthan the drawing roll 6 of the first unit, and the same is true withrespect to the feed roll 17 and the drawing roll 10. The top rolls arepressed down by conventional weighting means, as indicated by arrows(Fig. 4).

The zone between the two drawing stages of the twostage drawingmechanism extends from point 11 to point 12. In this zone, the sliver isin continuous contact with the rolls 6 and 7 (Figs. 1 and 2) or 5 and 7(Fig. 5) or with the rolls 6, l3 and 7 (Fig. 3); the first and lastrolls of these groups of rolls assume the double function outlinedhereinabove, and only a slight pressure is exerted on the sliver in thiszone so as to allow slipping of long fibers of the sliver.

Additional guiding rolls are shown in Fig. 3 at 13 and in Fig. 4 at 13,21 and 22. These rolls have a smooth surface when located between flutedbottom rolls of the drawing mechanism; when arranged in contact with asoftcovered top roll, the guiding roll should be fiuted as shown forroll 21 to ensure the proper gripping of the sliver. As will be readilyseen upon inspection of the drawings, the guiding rolls are so disposedas to exert some light pressure on the tangency lines with thecontiguous rolls; this ensures the transfer of the fibers but allowsslipping of any fiber already pulled by the following draft rolls.

The condensers which prevent fiaring of the fibers in those zones wherethe draft isproduced may be of known design and are represented by thenumeral 14 in the first drawing step, by 15 in the second drawing step,and by 23 in the third step (Fig. 4). 16 is the condenser which isnormally used at the intake of the sliver in the system.

A particularly'simple and compact embodiment of the invention is shownin Fig. 5 where the entire two-stage draft mechanism consists of 8rolls, a pair of feed rolls and a pair of draft rolls for either unit.In this embodiment the top feed roll of the first draft stage, the topdraft roll of the same stage, the bottom feed roll of the second draftstage and the bottom draft roll of said stage have the axessubstantially situated in the same plane, which feature constitutes apreferred but not necessary modification. The sliver which leaves thefirst drawing stage at 11 is first pulled around the surface of the topdraft roll of said first stage until it reaches the tangency line ofsaid draft roll with the bottom feed roll of the second drawing stage,and it is then pulled around the fluted surface of said bottom feed rollto the nip 12 of the pair of feed rolls 7, 8 of the second draftingstage. The sliver travels all the time on surfaces of revolving rollsfrom the exit 11 of the first drawing stage to the intake point 12 ofthe second drawing stage and is positively guided in an S shaped pathbetween points 11 and 12. The path of the sliver between the point 11and the drafting point 28 of the two drawing rolls of the second stageshould be somewhat longer than'the length of the longest fiber operatedon. This prevents breaking of the fibers and makes it unnecessary tochange at any time the position of the rolls 5, 6, 7, 8, 9 and 10 forworking up fibers of widely varying lengths. The roll 7 is driven at avery slightly higher peripheral speed than the roll 6; rolls 26 and 27designate conventional felt roils used as cleaners.

The described arrangement is suitable for any kind of spinning, draftingand roving frames, and it ensures a very high degree of control of thefibers during the whole travel of the sliver. It may be used to combinethe work of several drafting manipulations in a single compact unit forproducing a yarn of exceptional uniformity.

Although I have illustrated and described several forms of theinvention, it will be obvious that modifications can be made by anyperson skilled in the art without departing from the scope of theinvention as defined in the appended claims.

What I claim is:

1. A drawing mechanism for a strand of textile fibers comprising aplurality of drawing units', each of said units including a pair of feedrolls, a pair of drawing rolls and a condenser, and at least onerevolving guiding roll between a drawing roll of one unit and a feedroll of the next unit, said guiding rolls forming together with thesurface of said feed rolls and drawing rolls a continuous support forthe strand of fibers from its exit from one drawing unit to its intakeby the next drawing unit.

2. A drawing mechanism as defined in claim 1 wherein the axis of theguiding rolls is located above the plane in which the axes of thedrawing rolls and feed rolls contacting said guiding rolls are located.

References Cited in the file of this patent UNITED STATES PATENTS128,618 Harris July 2, 1872 317,675 Russell May 12, 1885 541,046 HarleyJune 11, 1895 2,203,423 Walsh et al. June 4, 1940 2,238,659 ReynoldsApr. 15, 1941 2,244,461 Kettley June 3, 1941 2,422,444 Balmes SolanasJune 17, 1947 2,472,929 Weinberger June 14, 1949 FOREIGN PATENTS 175,801Spain Nov. 23, 1946 649,109 Great Britain Jan. 17, 1951 693,422 FranceApr. 21, 1931

